Extensometer



oct. 26, 1943, P H HUME EXTENSOMETER Filed OCT.. 18, 1941 2 Sheets-Sheetl' 0d 26, 1943. P. H. HUME 2,332,797

EXTENSOMETER Filed Oct. 18, 1941 2 Sheets-Sheet 2 Patented 26, 1943nx'ransonm'raa Patrick H. Hume, Lakewood, Ohio, assigner toCarnegie-Iliinois Steel Corporation, a corporation of New JerseyApplication october 1a, 1941, serial No. 415,624

(ci. iso- 56) 13 Claims.

This invention relates to a method and means for determining the amountof elongation imparted to magnetic material, such as steel strip andwire, being rolled or drawn. The invention contemplates theaccomplishment of the measuring function while the work-piece isactually undergoing reduction, and further contemplates g the accuratemeasurement of elongation imparted per unit length of work-piece, and/orthe provision of means automatically to control the reducinginstrumentalities, to provide for the continuous production of strip orWire uniformly of the desired gauge.

In its general purposes, the present invention has relation to theco-pending application filed in the names of A. E. Hibschman et al. onOctober 1, 1941,A Serial No. 413,224, which is identiiied as a companionapplication, case A.

Specifically, the present invention differs from those disclosed in caseA in that it giveseffect to the purposes thereof without the needfor thepredisposition of a physical index marking upon the surface of thestrip, and by the use, in lieu thereof, of a magnetic indexing applied,as hereinafter described.

As will be seen from the following description, the present inventiontreats more specifically with a novel magnetic measuring device by whichany of the mill controls capable of altering the amount of reductionimparted to a work-piece, such as are disclosed in companion case A, canbe actuated thereby.

The instant disclosure does not, therefore, repeat the disclosures ofsuch mill control device effecting the decrease of compression andtension to which the Work-piece is subject, since this relationship willbecome obvious after the ensuing description is read, in light of thedisclosures made in the said pending application.

It is therefore, the primary object of the present invention to providea method andrneans for measuring elongated metal bodies -while they areundergoing reduction as by compression rolls or dies, without retardingor halting the reducing operation, and without physically marking ormutilating the work-piece in any manner.

It is a related object to correlate the measuring function either withsignal devices, the actuation of which indicates when proper and irn--proper'rolling conditions are in progress so that manual correctionthereof can be made, or with means automatically responsive to thecondition of the work-piece being reduced to maintain the reducinginstrumentalities adjusted to provide' the gauge desired.V

In the accompanying drawings, Figure 1 represents al schematic viewtaken in side elevation of a rolling mill, rolling strip to a thinnergauge in the direction of the arrows. It also includes circuit diagramsand physical appurtenances for giving effect to a simple embodiment oithe invention.

Figure 2 is a View corresponding to Figure 1, schematically showing arolling mill in the course of reducing strip with certainmagneto-electrical instrumentalities for applying the invention to theautomatic control of the screwdown mechanism of the rolling mill. To theright-hand side of this ngure, the strip and apparatus have beenenlarged more clearly to illustrate the principles of the invention.

Figures 3 and 4 represent modifications of cera tain elements of theinvention disclosed in Figure 2.

Referring now more particularly to the draw ings, in Figure l, the stripS is 'noved in the direction of the arrows, through reducing rollsi,which impart a reduction in thickness, and an extension in lengththereto.

At the approach side of the mill there are provided idle pinch rolls 2and 3, which co-act firmly to grip thestrip therebetween so as to bedriven by the movement of the strip without slippage.

suitably arranged upon a stationary support adjacent the pinch roll 2 ina switch mechanism fi, which comprises a switch arm 5 having contactbridging members 6 and i, respectively, carried at its opposite ends.The switch arm is pivoted intermediate its ends, as at 4a, to thestationary support, so that it is free to oscillate to carry the contactelements 6 and 'l into engagement with contacts 8--S, 9 9',respectively.

Oscillatory motion is imparted to the switch arm 5 through a link orpitman lil, which is pivoted at one of its ends to the switch arm, and,at its other end, is provided with a cam roller ii adapted to engage acam i2. The cam it is disposed in relation to the pinch roll 2 so as tobe driven thereby. The throw of the cam I2 is such as to move the switcharm from open circuit position to closed circuit position with respectto the contacts 8 8 and 9--9. The return of the switch to open circuitposition is assured by a tension spring I3, xed to the switch arm at oneof its ends, and secured to any suitable stationary support at its otherend.

The switch 4, when moved to dispose the movable contact element acrossthe contacts 8 8', closes a circuit comprised of leads i4 and I5, whichcarry direct current from any suitable source of supply, as has beenrepresented by the battery B, to electro-magnets I6 and Il disposed,respectively, upon opposite sides of the strip so that the north pole ofone of the magnets, when energized, registers with the south pole of themagnet upon the opposite side of the strip. Each of the electro-magnetsis provided with a core or stationary armature I 8 and l5, respectively,the proximate extremities of which areV tapered into a fine point spacedbut slightly from the strip moving therebetween.

From the foregoing, it will be seen that as the switch 4 opens andcloses the circuit I4 and I5, current from the battery B is induced toflow through this circuit to energize the electro-magnets I6 and I1 soas to set up a magnetic field of force through the strip and thus toestablish a local magnetic field in the strip at those points along itslength which happen by during the recurrent intervals when the switch 4is in closed circuit position.

This magnetic trace is established in the strip at the exit side oi' therolls from which it emerges in elongated condition. I'he frequency ofthe interval at which the local magnetic fields are established isdetermined by the rate of movement of the strip at the entry side of thereducing rolls translated into terms of rotary motion by the pinch roll2. As illustrated, the switch 4 is opened and closed once everyrevolution of the pinch roll 2, and at linear distances along the lengthof strip entering the mill equal to the circumferential extent of thepinch roll 2. The time in terval of establishing the marks is governedby the speed of travel of the entering strip, while the distance betweenmarks increases as the elongation thereof.

If the mill is not reducing the strip, the spots of magnetism placedthereon by the electro-magnets I6 and I1 would be spaced apart fromcenter to center, a distance equal to the circumference of the pinchroll 2. This distance ,can be measured in accordance with the presentinvention by disposing a take-off mechanism 20 the necessary distanceupon the down-stream side of the magnetic index establishingelectro-magnets I6 and I1. This take-olf mechanism may be thecounterpart of the latter by presenting electro-magnets 2I and 22 uponopposite sides of the strip having pointed core pieces 23 and 24disposed upon opposite sides of the strip in line with the magneticmarkings, so that the passage of the latter will establish temporarymagnetization of the corepieces so as to induce a current in .the lines25 and 26, which, at one end, terminate in the contacts 9 9' of theswitch 4, and, at the other end, terminate in the primary winding of aninduction coil or transformer 21.

Any current'induced in the primary winding 21 is similarly induced inthe secondary winding 28, which is in such relation to the primary. asto step-up the voltage thereof, and to pass such current through leads25'-26' to a relay R. The relay has an armature 29 to one end of whichis connected the lead 30 of a signal circuit, the

other end of which being adapted to close such circuit against thetension of the spring 3l upon energization of the relay R, wherebycurrent from any suitable source, such as is here represented bythebattery B, maybe permitted to ow and actuate a signal device 32, whichmay be in any suitable form.

In the foregoing description, it will be seen that, for the take-oilcircuit 25-26 to be energized by themagnetic markings established by theelectromagnets I6 and I1, two conditions must obtain: First, there mustbe a magnetic mark disposed between the points 23-24 of theelectro-magnets 2| and 22, and, secondly, the switch 4 must be in closedposition so as to cause the contact 1 to bridge the circuit contacts9-9' to complete the circuitof'the latter. Thus, it will be seen thatunless thefapprehension of the magnetic mark by *im electro-magnets2I-22 coincides with the closing of the circuit by the switch 4, nocurrent will be induced in the take-o3 circuit 25-2I. This means furtherthat the possible energizatlon of this take-ofi` circuit is synchronizedwith the establishment of the magnetic markings by the electro-magnetsI6 and I1, since the cam I2 actuates the switch arm 5 to close themagnetic mark establishing circuit, and the magnetic mark take-offcircuit, coincidentally.

The take-oil mechanism 20 is carried by a sliding frame 33 which issupported by stationary slide bearings 34 and 35, one of whichstationary slide bearings, illustrated to be 35, carries a iixeclV scale36 on which, by reference to a iixed index point 31 on the movable frame33, units of elongation are readable. Let it be assumed that the workrolls I of the rolling mill are not subjecting the strip S to anyreduction, then if the take-oil.' mechanism 20 is spaced from themagnetic establishing magnets I6 and I1 a distance corresponding to thecircumferential extent of the'pinch roll 2, or multiple thereof, thetake-oil mechanism will receive a magnetic impulse from a previouslyestablished magnetic mark simultaneously with the establishment of asucceeding mark by the electro-magnets I6 and I1.

Since, at the instant a magnetic marking is being established by theclosing of the contacts 8--8 by the contact element 6, the circuit 25-26is closed by the contact element 1 bridging the contacts 3 9', a currentis induced in the primary winding 21, which, in turn, induces a currentin the secondary winding 26 to cause actuation of the relay R to closethe associated signal circuit 30.

Let it now be assumed that the work rolls I impart some reduction to thestrip to extend it, a greater amount of strip per unit of time passesthe electro-magnets I6 and I1 than is required for the strip at theentering side of the mill to turn the pinch roll 2 one revolution. This.means that for the take-off circuit 25-26 to be energized by a magneticmark simultaneously with the establishment of such a mark by the magnetsI6 and I1, the take-up mechanism must be moved farther away from thelatter an amount corresponding to the extension imparted per unit lengthof strip by the work rolls I. The extent of this movement is readableupon the fixed scale 36 by reference to the line 31 on the movable'frame to give the actual amount of elongation being imparted to thestrip.

It will be understood that the simultaneous establishment and receptionof magnetic marks,

as is provided by the coordinating timing of the switch 4, is announcedby the recurrence of the actuation of the signal 32, the failure ofwhich to act indicates that the mill has, for various reasons, failed toimpart the required elongation.

When this o-gauge condition becomes apparent, the take-oil' mechanism 20maybe slid backward and forward along the slide bearings 34-35 until thesignal again resumes operation, at which point on the fixed scale 35,the operator can determine the direction and extent of departure fromgauge. Then, by resetting the slideable frame 33 of the take-oilmechanism to the desired setting, the operator may adjust the millaccordingly until restitution of the proper gauge is announced by thesignal.

In the embodiment shown in Figure 2, magnetic index establishing magnetsI5 'and I1 are provided to lay down a magnetic trace in the strip S, aspreviously explained in connectionl assays? with Figure 1. In this case,the pinch rolls 2 and 3 have .t been provided with synchronized current,commutatore 40-40, instead of the double throw switch 4 described inconnection with lFigure l. In the case or the pinch roll 2. brushes 4Iand 42 are arranged recurrently to energize the index-establishingmagnets I5 and I1 through the circuit i4|5, of which the battery B, orany other other suitable source of current, is a part.

The take-oil mechanism 20, instead oi being an individual magneticallyresponsive device, as previously described, comprises a gang of mov--ably mounted devices, constructionally and functionally similar to theone described in Figure l. In this case, however, the receiving magnetsare arranged in three groups: A center unit comprised of magnets 4545',and a gang grouping to each side of such center unit; those to the left,as viewedv in Figure 2, being represented by reference numerals 46-45',those to the right being represented by reference numerals 41-41'.

The center magnets 45-45' are arranged in circuit with a primary windingof an induction coil or transformer 48, the circuit of which is openedand closed through bus bars 25-25' by the commutator 40' associatedwiththe pinch roll 3. The primary winding 48 is associated witherl secondarywinding 49, which is provided with a suicient number of turns to step upthe primary voltage for the energization of a solenoid coil 50.

Each of the magnets 45-45' is provided with primary windings 5| whichcooperate with a common secondary winding 52 of an induction coil ortransformer, the leads of which secondary are applied to a solenoid coil53. The circuit of each of the magnets 46-45 is opened and closedthrough the vbus bars 2526' by the commutator 40 as in the case of thepreviously described central magnetic circuit.

The magnets 41--41' are similarly provided with primary circuits, whichare commutated through the bus bars 2525' by the commutator 40, throughwhich the secondary windings 54 of each are energized. A secondarywinding 55 is associated with the primary windings 54, in the circuit ofwhich secondary is ineluded a solenoid coil 55.

Each of the solenoid coils 50, 53, and 55, is provided with an armature51, 58, and 59, respeotively, which are connected together for unitarymovement by non-magnetic portions 50. Suitably connected to the armatureassembly, as

yby a non-magnetic extension 5I, is a switch 52,

which comprises an oscillatory arm 83 pivoted intermediate its ends, asat 64, for movement v between contacts L1 and In to which it is adaptedalternately to connect one side of an electrical circuit represented bythe lead L. The switch arm 63 is movedin response to movement of thearmature assembly by being connected to the extension 6I thereof as at55,.

A Areversingrmotor 55 is provided to receive energizing current from theleads In: and L, the latter of which is connected through either thelead L1 or the lead In to drive the motor in clockwise orcounter-clockwise direction, as the case maybe. The drive shaft of themotor is shown schematically as being connected, as at 61, to drive abevel pinion 58, which, in turn, is adapted to drive a bevel gear 69 ofthe screwdown mechanism of the mill of which the work rolls i are a partThe leads L1 and La may, instead oi actuating the screwdown mechanism ofthe mill as shown, be directed to control either the pay-oi! reelgenerator, or the take-up reel motor. to vary the tension in the stripbeing reduced in a manner, and for the reasons, set forth in thecompanion application hereto, case A, previously mentioned. In thismanner, its applicability to a tension wire drawing operation through adie is apparent. As in case A, both the compression and tensioncorrections may be simultaneously applied when rolling strip, or itsequivalent.

The operation of the device is as follows: As the strip is moved in thedirection of the arrows through the kreducing rolls I, the magneticindex is established therein by the magnets I6 and I1 at a ratedetermined by the speed o! the strip at the entering side of the mill,by which, through the pinch roll 2, the electrical current circuit |4 I5is commutated.

The pick-up mechanism 20 will have been predisposed at a suitabledistance (corresponding to gauge extension, as explained in Figure 1)from the establishing magnets IB and l1 in such manner that, when thecommutator 4i!y is in closed circuit position relative to the magnets i6and I1, and the commutator 40 is in closed circuit p0- sition relativeto the pick-up magnets 20; a predisposed index mark will be between thepoints of the center magnets 45-45'. When this is done, the material ison-gauge. and a current will be induced in the primary circuit 48 in thesecondary circuit 49 in the center magnets so as to energize the coil 50to position the armature 51 entirely within the coil, where it reducesthe magnetic reluctance of the magnetic circuit thereof to a minimum. Inthis center position, by means of the non-magnetic connections 55 and6I, the adjacent armatures 58 and 59 would be disposed toward the centercoil approximately one-half way within their respective coils-53 and 55,andthe switch arm 63 would be poised midway between the lead contacts L1and Lc. In this condition, the circuit to the motor 86 is accordinglyopen, and no screwdown operation is effected.

Let it be assumed that the strip being rolled is subjected to insulcientreduction, then its elongation is accordingly shortened, so that, whenthe commutators 40-40 establish an index mark and close the circuits ofthe take-off mechanism 20, a. preceding magnetic index mark will notfall beneath the center magnets 45 and 45' of the take-ofi.' mechanism,but will be somewhere within the range of the take-oil' magnets 46-45'.Therefore, during the interval at which the commutator 40' maintains thetake-oil circuits closed,

the magnetic index mark magnetizes a pair of the magnets 46--45'inducing a current to iiow momentarily in the primary windings 5I of theassociated circuit. This, in turn, induces a current in the secondary52, energizes the solenoid coil 53 so as to attract its armature 58, anddraws the armature, and its associated assembly, leftwardly. This movesthe switch arm 53 to connect the lead L with the lead La to drive themotor 55 in a direction so as to increase the screwdown pressure exertedby the work rolls I upon the strip. The strip will thus be elongated agreater amount.

The correction will continue to be applied until the closing oi thetake-up circuits by the commutator 40 is eilected simultaneously withthe presence of a magnetic index mark within the effective range or thecenter magnets 45-45@ When this happens, the proper gauge condition hasbeen restored, and is thereafter preserved by the ensuing energizationof the coil 50, through the primary 48 and secondary windings 48 of thecenter magnets, which causes the armature 50 tc return from itsleftwardly displaced position of the assumed example, to the center ofthe coil, as previously mentioned. When this is done, the switch arm 63is returned to open position, midway between the contacts L1 and La.

If the strip were being given too much extension, a similar operationwould be effected through'the magnets 41-41', the primary and secondarycircuits 54 and 55 thereof, respectively, and the coil 56. In this case,the amature 58 would be drawn rightwardly, as shown in Figure 2, intothe coil B, so as to reduce to a minimum the reluctance of the magneticcircuit of that coil, simultaneously withdrawing the armature I1rightwardly to a position about half way out oi' the coil 50, and lthearmature 54 almost entirely out of its associated coil 53, in the samedirection. This would cause the switch arm 83 to connect the lead L withthe lead L1 so as to energize the motor to operate in a directionopposite to that previously described, thus to effect a relieving of thecompressive force of the rolls l. vThe correction is continued until amagnetic mark lies Within effective distance of the center magnets45-45', which causes the coil 50 to be energized so as to return thearmature assembly and switch arm 83 to neutral position, as previouslydescribed. As shown in the aforementioned companion application, case A,the screwdown pressure may be substituted or replaced by a correctionimposed by varying the tension to which the strip is being subjected, inwhich case, the leads Li and La would be in a relay circuit capable ofvarying the field resistance of either the take-up reel motor or thepay-orf reel generator, all as set forth in that'application.

In Figures 3 and 4, there are shown simplified embodiments of the deviceof Figure 2. In Figure 3, the magnets 46-46 and magnets 41-41' arebrought together so as to provide two magnets 1li-1|, respectively, eachhaving an annular core 12 and 13, respectively, designed to present anelongated pole 14 parallel to the surface of the strip and closelyadjacent thereto. The pole faces 14 extend over an area of strip in alongitudinal direction substantially commensurate with the gang ofmagnets illustrated at 20 in Figure 2. The central magnet has anabbreviated pole face 15, and is arranged in contiguous relation tomagnets and 1| The magnet 10 is provided with a primary circuit 5|, asecondary circuit 52, and a solenoid coil 53, the same as described inthe case of Figure 2'. The center magnet 15, and the right-hand magnet1|, al1 similarly provided with primary and secondary circuits, the sameas disclosed in Figure 2, by virtue of which the same reference numeralshave been applied. The armature arrangement, the motor control switch62, and associated parts, being as they are similarto those disclosed inFigure 2, have been marked accordingly, as will not be redescribed.

When an index mark passes beneath the pole face 14 of either of themagnets 10 or 1|, a current is induced in the associated primary andsecondary circuits Aas previously described so as to cause a compressionor tension correction of the strip to be instituted accordingly.

Figure 4 illustrates another arrangement which effects somewhat of acompromise between the take-olf devices of Figures 2 and 3. As in Figure2, several magnet windings are provided to serve individual primarywindings, but as in Figure 3, more or less unitary pole faces arepresented to the strip. Since the same reference numerals `have beenapplied to Figure 4 to signify parts corresponding to those disclosed inthe other figures, no further description of the Figure 4 modificationis deemed necessary.

Accuracy of operation requires that the commutation of the indexestablishing current, which also determines the rate of take-off, be nomore than will provide for the passage of. but one index mark at a timewithin the longitudinal limits of the assembly of take-oi! magnets shownin Figures 2', 3 and 4. Thus, no matter where the mark may fall when thevtake-oil circuits are closed, the correction must be such as to returnthe ensuing magnetic marks toward the central magnets, there to bring toa halt the correcting function.

The distance at which the magnets, disclosed in Figure 2, should bespaced apart longitudinally of the strip is determined by with whatdegree of criticalness it is desired to control the gauge of the stripbeing produced. If the commutation of current at the entry side of themill is such as to' establish a magnetic index mark every one foot .ofstrip, as unreduced, and the points of the magnets 45, 46 and 41, andtheir respective primes, are spaced a quarter of an inch apart, thereduction in area will be controlled to within 1% of the gauge setting.Thus, by way of example, it could be assumed that strip of .010 gauge isbeing rolled, and is being indexed so as to place the localized magneticmarks one foot apart, the 1A variation in extension (which is 2'% of theunit length) equals approximately 1% reduction in area, as mentioned,or, for this size stock, would amount to one-ten thousandths of an inch(0001") reduction in thickness. This is a working tolerance far morecritical than that obtainable from any of the devices now being usedcommercially for similar purposes.

If it is desired to control percentages of extension less than 1%, it isbut necessary to enlarge the circumferential extent of the pinch roll 2,or otherwise to decrease.-A the commutation rate thereof, whilemaintaining the spacing between the take-oi! (magnets, substantiallyconstant. This will have the eilect of disposing a greater linear extentof strip between the magnetic index marks, in relation to which the V4spacing of the take-off magnets will be relatively diminished, thuscreating a Vernier effectWfor the more critical determination ofincrements or decrements of elongation per unit length of strip.

It will be understood that the take-off magnets will be predisposed inrelation to the index establishing magnets so that, when the strip isundergoing no reduction, the central magnet will fall that distance fromthe index establishing magnets equal to one complete commutating cycle,or multiple thereof, of the commutator 4II, as determined by the degreesof revolution ot pinch rolls 2 and 3 revolving without slippage upon thestrip as it approaches the mill.

At one foot between centers of adjacent index marks at no reduction,then, for every J/. which the take-off magnets are moved away from theestablishing magnets to maintain coincidence between the establishmentand apprehension of index marks, the strip will have been subjected to1% reduction of-its cross-sectional area. In the assumed example of.010" gauge strip, such V4" movement of the take-olf magnets would berepresentative of the fact that the mill was imparting that reductionamounting to .0001" reduction in thickness. Such presetting of thetake-off magnets may be accomplished by a reference point movabletherewith in relation to a iixed gauge 36, similar to that shown anddescribed in Figure 1.

It will be understood, therefore that many modiiications of theinvention may be made without departing from the scope thereof, and itis not intended that I be limited to the speciiic embodimentshown, otherthan as is rendered necessary by the recitations of the appended claims.

I claim:

1. An extensometer for combination with a mill ior reducing andelongating metal bodies comprising a magnetizer for establishing localfields of magnetism in a metal body after reduction, a timer actuatingsaid magnetizer at intervals determined by the rectilinear velocity ofsuch a body before reduction, and'magnetically responsive means undercontrol of said timer and responsive to the local fields of magnetism inthe body for determining the amount of extension imparted to said body.

2. An extensometer comprising a magnetizer` for establishing localiields of magnetism in a metal body undergoing reduction, a magneticallyresponsive take-ofi device adapted to be excited by said local fields ofmagnetism, and a timer driven by the metal prior to its reduction, saidtimer being effective to synchronize the operations of said magnetizerand said device.

3. An extensometer for combination with a mill for reducing andelongating metal bodies comprising a magnetizer for establishing localfields oi magnetism in a metal body after reduction, a timer actuatingsaid magnetizer at intervals determined by the rectilinear velocity ofsuch a body before reduction, magnetically responsive means undercontrol of said timer andresponsive to the local elds of magnetism inthe body to control the mill so as to correct automatically off-gaugesettings thereof, and to maintain the correct reducing condition.

4. An extensometer comprising a magnetizer for establishing local fieldsof magnetism in a metal body undergoing reduction, a magneticallyresponsive take-on device adapted to be excited by said local fields ofmagnetism, and a timer for rendering the magnetizer and take-oil deviceoperable synchronously.

5. An extensometer comprising a magnetizer for establishing local fieldsoi magnetism in a metal body undergoing reduction, a magneticallyresponsive device movable with respect to said magnetizer adapted to beexcited by said local fields of magnetism, means for effectingsynchronous operation of said magnetizer and said device and measuringmeans actuable by the movement oi said device.

6. An extensometer for combination with a mill for reducing andelongating metal bodies comprising a magnetizer disposed upon the exitside oi the mill for placing magnetic marks in such a body, a timerdisposed upon the entrance side of the mill adapted to be actuated bythe entering body for operating saidmagnetlzer, and means responsive tothe magnetic marks in the body for determining the extension impartedthereto.

7. An extensometer for combination with a mill for reducing andelongating metal bodies comprising a magnetizer disposed upon the exitside of the mill for placing magnetic marks in such a body, a timerdisposed upon the entrance side of the mill adapted to be actuated bythe entering body for operating said magnetizer, means responsive to themagnetic marks to detect ongauge, under-gauge, and over-gaugeconditions, and means responsive to the last-named means for actuatingthe mill to preserve on-gauge conditions, and automatically to correctoff-gauge conditions, whether overor under-gauge, to establish theproper reducing condition.

8. The method of reducing metal stock which includes passing stockthrough a reducing zone, magnetically marking the stock upon the exitside of the zone, automatically measuring the distance between certainof said marks and controlling the reducing operation by saidmeasurements in an automatic manner.

9. The method of reducing an elongated metal body which includesmagnetizing spaced local iields on said body, measuring the amount ofextension imparted thereto between adjacent magnetized iields during thereducing operation, and regulating the amount of reduction automaticallyin response to the said measuring operation.

10. The method of measuring elongated metal bodies during the reductionthereof which includes magnetically indexing the reduced body at a ratedetermined by the speed of advance of the unreduced body.

11. The method of reducing elongated metal bodies which includesmeasuring the amount of extension imparted thereto incident to thereducing operation by indexing a metal body after it has left thereducing means according to its rate of advance to said means, passingthe indexing past mechanism responsive thereto, to measure the extent ofreduction and to detect whether the reducing operation is reducing thebody the desired amount, and automatically correcting the reducingcondition in response to the measuring operation if more or less thanthe desired reduction is being imparted to said body.

12. Means for determining the amount of extension imparted to a metalbody during the reduction thereof including an index establishingdevice, a plurality of detector mechanisms actuable in response to theindexing established by said device to detect under-gauge, on-gauge, andover-gauge conditions, and means operable in response to the movement ofthe body upon the approach side of the reducing operation for renderingsaid device land said mechanisms operative simultaneously.

13. Means for controlling the reduction of long metal bodies undergoingreduction by a reducing instrumentality comprising an index establishingdevice, a magnetic under-gauge detector mechanism, an over-gaugedetector mechanism, means automatically responsive to the operation ofsaid detector mechanisms for controlling the reducing instrumentality todiminish and increase the amount of reduction imparted to the body torestore desired gauge conditions, and means responsive to the magneticindexing established by said device for terminating the operation ofsaid last named means upon the attainment of desired gauge conditions. y

PATRICK'H. HUME.

